Most theftproofing systems today consist of a combination of an ignition-starter lock and a mechanism which blocks the steering. The mechanism, when or after the ignition key is removed, pushes the locking member into the recess of the locking ring firmly connected to the steering shaft. A disadvantage is the fact that the theftproofing system can be overcome by the use of force by introducing external forces through the steering wheel into the steering shaft which lie above the limiting torque and thus remove the block, which destroys the locking member or breaks out the recess in the closing ring. Another disadvantage is the fact that, in the case of theft, the entire steering mechanism is damaged and, if the car is ever recovered, the steering can only be repaired at great cost.
From German patent DE 39 05 183 A1 a theftproofing system for motor vehicles is known in which the steering wheel has another lock and a locking device which can be brought into the active position by the steering shaft in such a way that the lock in a first position creates a rotation-proof connection between the steering wheel and the steering shaft, and in a second position this rotation-proof connection is broken. Motor vehicles displaying conventional theftproofing systems can be additionally equipped by this other theftproofing system which is intended exclusively for the steering wheel.